An interesting article here. Apparently 100 years ago: "the generally accepted rule is pink for the boys, and blue for the girls. The reason is that pink, being a more decided and stronger colour, is more suitable for the boy, while blue, which is more delicate and dainty, is prettier for the girl." https://www.theguardian.com/theguardian/2009/dec/12/pinkstinks-the-power-of-pink